1. Field of the Invention
The present invention generally relates to a wrist exerciser that is held by a palm of a user and having an internal rotor that is caused to rotate by the user exercising his or her wrist muscles, and in particular to a device for enhancing force balance and reducing vibration caused by the operation of the wrist exerciser.
2. The Related Art
A wrist exerciser is employed to exercise and rehabilitate wrist-related muscles of a user. Apparent therapeutic result can be obtained in the user for rehabilitation purposes. Examples of the wrist exercisers are shown in Taiwan Utility Model No. 135058 and U.S. Pat. No. 5,800,311, both disclose wrist exercises in which wrist related muscles are well exercised by simply rotating the wrist exerciser with the wrist.
FIG. 10 of the attached drawings shows a conventional wrist exerciser, which is designated with reference character A, comprising a rotor A1 encased in a spherical casing constituted by upper and lower hemi-spherical casing members A2, A3. A circumferential groove A11 is defined around the rotor A1. A hole A12 is defined in the rotor A1 inside the groove A11. The upper casing member A2 defines an opening A21 substantially corresponding in position to the groove A11 for the extension of a rope B. The rope B is wound around the rotor A1 by being received in and extending along the groove A11. When the rope B is quickly withdrawn out of the rotor A1, the friction between the rope B and the rotor A1 causes the rotor A1 to rotate inside the casing.
The rotor A1 is rotatably supported inside the casing by two axles A13 extending from opposite sides of the rotor A1 in opposite directions. The axles A13 are rotatably received in holes (not shown) defined in the casing. The axles A13 is smaller in weight, diameter, and length than the rotor A1 itself, which leads to force unbalance during the rotation of the rotor A1. Further, the axles A13 may induce resonance due to the high speed and high torque rotation of the rotor A1, leading to significant vibration of the axles A13 and abrasion with the casing members A2, A3. This shortens the service life and also generates large noise. Further, the vibration makes it difficult for a player to firmly hold the wrist exerciser A during the operation of the wrist exerciser A. A11 these result in difficulty and inconvenience in operation.
Thus, it is desired to provide a wrist exerciser that overcomes the above deficiencies of the conventional wrist exercisers.